1. Methods expressing Concentrations of solutions IIBy
All Staff Members of
Medical Biochemistry Department

2. 1-Apply different methods for expressing concentration
By the end of this topic, the student will be able to:
1-Apply different methods for expressing concentration
2-Perform different dilutions from stock solution.

3. 3- Normality (N) gm equivalent / L
The number of gram-equivalents of solute in one liter of solution.
A normal solution contains 1 gram-equivalent weight of solute in a liter of solution.

4. What is gram equivalent ?
A gram equivalent weight (G.E.W.) of an acid or a base is the molecular weight in grams of the solute required to react, or replace one mole of H+ or OH-.
1 mole of Na+1 = (1 N).
1mole of Ca+2 = (2 N).

5. Weight of 1 G.E.W= Molecular weight Valency
Weight of A gram-equivalent (G.E.W) of an element
= MW of the solute in gram (1mole) / Valency
which is the number of replaceable hydrogen or hydroxyl ions.
Weight of 1 G.E.W= Molecular weight
Valency

6. 1N solution = a solution contains
Normal Solution
1N solution = a solution contains
1 G.E.W/ L.

7. Examples
Monovalent acids or bases
HCL - NaOH- Nitric M = IN
Divalent acids
H2SO M = 2N
Trivalent acids
Orthophosphoric acid 1M = 3N

8. Normality = Molarity x Valency
Normality of 1M H2SO = 1 x 2 = 2 GEW/L
Normality of 1M HCl = 1 x 1 = 1 GEW/L
Normality of 1M H3PO = 1 x 3 = 3 GEW/L
Normality of 0.4M H3PO4 = 0.4 x 3 = 1.2 GEW/L
Normality of 0.2M NaOH = 0.2 x 1 = 0.2 GEW/L

9. Examples Prepare 1 normal solution of NaCl
[MW of Na= 23 & of Cl = 35.5]
MW of NaCl= = 58.5 g
G. E. W. = 58.5g
Thus, a solution of 1N NaCl contains
58.5 g of NaCl / 1 L.

10. Prepare 1 normal solution of CaCl2
[MW of Ca= 40 +Cl = Cl = 35.5]
MW of CaCl2 = = 110g
G. E. W. = 110g/2=55
Thus, a solution of 1N CaCl2 contains
55 g of CaCl2 / 1 L.

11. Normality = Molarity x Valency
What is the normality (N) of 0.3 M orthophosphoric acid?
Normality = Molarity x Valency
0.3 x 3 = 0.9 N

12. Inter-Conversion of units
To convert between gram and mole we have to know the MW
Number of Mole= Weight (g)
MW (g)
To convert between M and N, we have to know the valency.
Normal= Molarity x valency

13. Example:
What is the plasma urea concentration in mmol/L corresponding to 20 mg/dL? (m.w. of urea = 60)
Answer
Conc. of urea in mmol /L = 20/60 = mmol/dl x 10 = 3.33 mmol/L

14. Example:
What is the plasma sodium (Na+) concentration in mmol/L (mM) corresponding to 140 mEq/L (mN)?
Answer
Conc. of (Na+) = 140 mmol/L

15. Summary

16. 4- Very low concentrations
Expressing concentrations in parts per million (ppm) requires the unit on top to be 1,000,000 times smaller than the unit on the bottom.
It is used to measure trace substances in solutions or mixtures, eg. mg/kg, µg/g.
Cl Concentration in swimming pools.

17. Dilutions
You dilute a solution whenever you add solvent to a solution.
Adding solvent results in a solution of lower concentration.

18. You can calculate the concentration of a solution following a dilution by applying this equation:
CiVi = CfVf
Where:
C =concentration,
V = volume
i =initial value.
f =final value.

19. Dilution Factor:
Is the ratio of the final volume to the original volume.
If 10 ml of blood are completed to 100 ml with saline, we say that blood is diluted 1 in 10, and the dilution factor is 100 / 10 = 10
The dilution factor =
Final volume / original volume.

20. Example:
How many milliliters of 5.5 M NaOH are needed to prepare 300 mL of 1.2 M NaOH?
Answer : 5.5 M x Vi = 1.2 M x 0.3 L Vi = 1.2 M x 0.3 L / 5.5 M Vi = L= 65 mL
So, to prepare the 1.2 M NaOH solution, you add 65 mL of 5.5 M NaOH into your container and add water to get 300 mL final volume.

21. Summary of Concentration units
Symbol
Definition
Mass Percent
% m/m
mass solute/mass solution x 100%
Volume Percent
% v/v
volume solute/volume solution x 100%
Mass / Volume Percent
% m/v
mass solute/volume solution x 100%
Molarity M
moles solute/L solution
Normality N
Gram equivalent/L solution
Part per million
ppm

22. Lab activities
Prepare 100 mL of 0.1 M NaCl from stock solution 1 M.

23. Important equations
V1 × C1 = V2 × C2
N = M × V
M = moles / liter
G E W= MW/V

25. Extended Modular Program